afs commented on issue #3345:
URL: https://github.com/apache/jena/issues/3345#issuecomment-3114836545

   So you are getting `TimeoutException` on download (backup) and upload 
(restore) cases?
   
   `java.util.concurrent.TimeoutException` isn't from Jena itself.
   
   "(client left?)" is Jena - it is part of a general catch for all kinds of 
network errors and they are commonly because the connection to the the client 
stopped responding (did not close the connection neatly) but that is not what 
is happening here. teh server used to print the stacktrace but clients leaving 
is something that happens in normal use and the logs fill up.
   
   The project has encountered a situation that might be related but only in 
the test suite and only when running as a github action.
   
   One or two tests occasionally fail on some kind of low level timeout in the 
JVM networking code. We don't know why - a guess is that the machine it is 
running on is a heavily loaded and shared server, and the host VM has a very 
long pauses due to kernel scheduling. In the past, we've seem quite long pauses 
(30s+) in scheduling.
   
   In this situation they may be a compounding effect. `application/trig` is 
trying to output "pretty" trig by running the Turtle pretty printer on each 
graph. That is can be expensive in CPU and during preparation the network isn't 
being used. Combined with pauses, that might push something over the edge.
   
   Unfortunately, there isn't a way to ask for one of the forms of TriG that is 
less costly. (Maybe, Jena should use one such for this case of dataset-trig 
output.)
   
   Suggestion: use n-quads for backup. This is streaming and efficient and it 
does not have a potential long network pause.
   
   Questions:
   1. What environment is this running in? A cloud provider?
   1. Is there a proxy or gateway between curl and the Fuseki server?
   
   There are some comments on the Jetty issues related to failed connections 
interfering with connection management but they only look "maybe related"  to 
me.


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